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From "Stefania (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-9673) Improve batchlog write path
Date Fri, 17 Jul 2015 02:21:04 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-9673?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14630677#comment-14630677
] 

Stefania commented on CASSANDRA-9673:
-------------------------------------

The user profile is correct, I verified with a temporary debug line that SP.syncWriteToBatchlog()
is executing.

With progressively bigger tests it gets clearer however that the GC times improve with the
patched version. I've attached the results with *n=500000*, file 004, along with the JMC screenshots
of the GC times of the first node. 

> Improve batchlog write path
> ---------------------------
>
>                 Key: CASSANDRA-9673
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-9673
>             Project: Cassandra
>          Issue Type: Improvement
>            Reporter: Aleksey Yeschenko
>            Assignee: Stefania
>             Fix For: 3.0.0 rc1
>
>         Attachments: 9673_001.tar.gz, 9673_004.tar.gz, gc_times_first_node_patched_004.png,
gc_times_first_node_trunk_004.png
>
>
> Currently we allocate an on-heap {{ByteBuffer}} to serialize the batched mutations into,
before sending it to a distant node, generating unnecessary garbage (potentially a lot of
it).
> With materialized views using the batchlog, it would be nice to optimise the write path:
> - introduce a new verb ({{Batch}})
> - introduce a new message ({{BatchMessage}}) that would encapsulate the mutations, expiration,
and creation time (similar to {{HintMessage}} in CASSANDRA-6230)
> - have MS serialize it directly instead of relying on an intermediate buffer
> To avoid merely shifting the temp buffer to the receiving side(s) we should change the
structure of the batchlog table to use a list or a map of individual mutations.



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